Northern Midland Basin Research Articles

Seismic attribute and well-log analysis for channel characterization in the upper San Andres and Grayburg formations of the Midland Basin, Texas

The Permian Basin is one of the most prolific, and currently one of the most active, oil and gas basins in the USA. The Lower Permian strata in the Permian Basin have produced more than 14 billion barrels of oil (BBO), making it the largest volume of hydrocarbon in the basin. Sedimentation in the Midland Basin during late Leonardian through early Guadalupian (ca. 272–269 Ma) resulted in progradation of shelf edge and ultimately closure of the basin by Middle Permian time. We analyzed a merged seismic survey covering parts of the Permian Basin (i.e., Central Basin Platform and Midland Basin) in Andrews, Ector, and Midland Counties, Texas. The seismic survey and well logs show the presence of gently dipping (ca. 1°) clinoforms in the Upper San Andres and Grayburg Formations on the eastern edge of the Central Basin Platform and western Midland Basin. The seismic attributes, curvature, and spectral decomposition identify low sinuosity slope channels oriented north-south, but such channels do not appear beyond the slope. The shelf edge shifts from north to south during deposition of the Upper San Andres and Grayburg Formations. We identify five basinward shifts noted by the migration of the shelf edge toward the basin center and the presence of channel features along the depositional slope. The petrophysical analysis indicates that channels cut into carbonate rocks and are filled by siliciclastic sediments; this interpretation is supported by the most negative curvature anomalies along the channel axes caused by the differential compaction between the carbonate and siliciclastic rocks. There are a few channels with a northwest-southeast strike, which matches the direction of the Concho Lineament observed by satellite data. Such observations are consistent with previous interpretations of the northern Midland Basin closure during Middle-Late Permian time.

Technology Focus: Field Development (September 2022)

In this month’s Field Development feature, SPE conference authors place an emphasis not only on original research and findings but also on validation and refinement of existing techniques that may not have received thorough attention in the literature. As operators strive to achieve the greatest returns possible from technically, environmentally, and economically challenging plays, they are driven to innovate new approaches and to fine-tune existing ones. In paper SPE 206267, the authors investigate the performance of a distributed quasi-Newton (DQN) derivative-free optimization (DFO) method, which, they write, had not yet been validated by realistic applications or compared with other DFO methods. They integrate DQN into a versatile field-development optimization platform designed for iterative work flows enabled through distributed parallel flow simulations. The method was field-tested on two realistic applications and identified the global optimum with the least number of simulations and the shortest run time on a synthetic problem with a known solution. The authors of paper SPE 207146 create and evaluate a development plan for an oil field discovered in a remote offshore environment in the Niger Delta. Because the oil in place was uncertain, a probabilistic approach was used to estimate the stock-tank oil originally in place using low, mid, and high cases. Keeping in mind governmental regulations to maintain the reservoir pressure above bubblepoint, the authors propose a development plan that is marginally base modeled and, despite the uncertainty of oil prices in the market, able to cover any unforeseen situations. Finally, the authors of paper SPE 208882, addressing the challenge posed by cumbersome integrated technical work flows for multiwell fracture modeling and reservoir simulation, use tools existing in the literature to quantify the effect of changing well spacing on well productivity for a given completion design using a simple, intuitive empirical equation. After describing and qualifying the use of their approach, they apply it to a case study from the Permian Basin. Recommended additional reading at OnePetro: www.onepetro.org. OTC 31151 - Autonomous Subsea Field Development—Value Proposition, Technology Needs, and Gaps for Future Advancement by Giorgio Arcangeletti, Saipem, et al. SPE 206533 - Field Development Optimization Using Machine-Learning Methods To Identify the Optimal Waterflooding Regime by Alexey Vasilievich Timonov, Consultant, et al. URTeC-2021-5301 - Unconventional Reservoir Development Performance Reviews—the Northern Midland Basin Case Study by Hongjie Xiong, University Lands, et al.

Integrated detection and investigation of bad borehole section in the Wolfcamp Formation in the Midland Basin using machine learning, petrophysics, and core characterization

The quality of formation evaluation and reservoir estimates depends a lot on the quality of open hole logs, which is intricately tied to the borehole geometry and stand-offs. Bad borehole sections cause interesting patterns on wireline logs that can result in multiple interpretations. We have conducted an automated identification of bad borehole sections (>50 ft [15 m] thick) in multiple wells in the Wolfcamp Formation in the Midland Basin of the United States and investigated the causalities behind the unstable borehole section. The wells impacted by bad hole conditions appear to be within a particular region of the northern Midland Basin, and the bad hole condition impacts a specific zone in the Wolfcamp D. We consider well logs as multivariate time series (or depth series), where they share interdependencies to a large extent. We use this concept and unsupervised multivariate time series clustering to automatically identify bad borehole sections. Our proposed workflow simultaneously clusters the wireline logs, resulting in a large labeled regional-scale data set that can be further used for log quality assurance, processing, and petrophysical modeling. More importantly, we investigate the reasons behind the borehole washout, integrating sedimentology and geochemical data. Thick borehole washout sections are related to the presence of a significant amount of clay (>73 wt%, a mixture of smectite and illite) in the Wolfcamp D. The results also indicate that the manual editing of wireline logs and even supervised machine learning-based log reconstruction (commonly known as a missing log prediction problem) can lead to erroneous and inconsistent interpretation of subsurface characteristics. Such exercise can be meaningless if derived models are not validated with the ground truth (preserved subsurface rocks). Geologic feature: Clay-rich unstable borehole section Log appearance: Large-to-small caliper response associated with erratic density and neutron porosity logs Features with similar appearance: Gypsum, siderite nodules, and tool failure Formation: Wolfcamp Formation Age: Wolfcampian Location: Northern Midland Basin, Texas, USA Well data: Obtained from the IHS Analysis tools: Unsupervised machine learning, core description, geochemistry, and petrophysical inversion modeling

Conodont and fusulinid biostratigraphy of the Strawn Group (Desmoinesian, Middle Pennsylvanian) and lower part of the "Wolfcamp Shale" (Missourian-Virgilian, Late Pennsylvanian) in the northern Midland Basin, West Texas

Conodont and fusulinid biostratigraphy of the Strawn Group (Desmoinesian, Middle Pennsylvanian) and lower part of the "Wolfcamp Shale" (Missourian-Virgilian, Late Pennsylvanian) in the northern Midland Basin, West Texas

Dolomitization of periplatform carbonates (Lower Permian, Leonardian), Midland basin, Texas

Dolomitization in three cores of Lower Leonardian, periplatform carbonates in the subsurface Midland basin post-dated mineralogic stabilization and calcite cementation, which occurred in the deep-sea, shallow-burial (<2000 ft subbottom: 610 m) environment. Mean δ18O compositions of dolomites from two of the cores located in the northern Midland basin are slightly depleted relative to presumed Lower Permian seawater (°18O=−2.65 o/oo and −1.85 o/oo, respectively), but overlap those of associated precursor limestones and prior-precipitated calcite cements (δ18O=−2.6 to −3.1 o/oo). Carbon isotopic compositions of these dolomites define a limited range of positive δ13C values (1.5 to 2.3 o/oo). Isotopic and trace-element data suggest initial dolomite formation in the shallow-burial, subbottom environment, in the absence of sulfate reduction or methanogenesis, in rock-dominated diagenetic systems. Mean oxygen and carbon isotopic compositions of dolomites in the third core, located in the east-central Midland basin, are more depleted (δ18O=−4.1 o/oo; δ13C=3.3 o/oo). Isotope and trace-element data also suggest initial formation of these dolomites in the shallow-burial, subbottom environment, but from marine fluids depleted in δ18O as a result of the prior precipitation of calcite cements. Dolomitization in all three cores began in the Permian, at subbottom depths perhaps as shallow as 2000 ft (610 m). Sr isotopic data, in conjunction with the burial depth-temperature history of these wells, suggest that dolomite formation and recrystallization were complete by the end of the Permian, when the rocks were buried to about 6000 ft (1830 m). Subsequent diagenesis, which included significant porosity creation via dissolution, occurred in the deeper mesogenetic environment during the Mesozoic.

Petrographic image analysis and petrophysics: Analysis of crystalline carbonates from the Permian basin, west Texas

Classification of porosity in carbonate rocks from thin section can be performed quickly and objectively using computer-based image acquisition and classification procedures. Pore type information (size, shape and volumetric abundance) is determined with high precision, equivalent to millions of point counts. Such pore type information is always relevant because each pore type has a different distribution of associated pore throat sizes. Five pore types occur in a sequence of highly recrystallized dolomites from the Reinecke Field in the Late Carboniferous Horseshoe Atoll Complex in the northern Midland basin. These pore types represent an expanded version of conventional classification, representing two kinds of intercrystalline porosity and three kinds of channel porosity. The channel pore types represent secondary porosity which survived cementation by dolomite, and can be classified into channel pores of three distinctly different sizes. When combined with capillary pressure data the image-based pore type data reveals that the intercrystalline pores have very small throats while the channel pores have throats which are closer in size to the pore body. The product of the numbers of pores per unit volume of each type and the fourth power of the associated mean throat diameter is an index of the relative contribution of each pore type to discharge. In the Reinecke Field rocks, the smallest type of channel pore is the major control on flow. Its relatively small throat size is compensated by its great numerical abundance. The preference of throat size for pore type in these highly recrystallized dolomites, is just as strong as previously observed in detrital sandstones. Relatively tight limestones found with the dolomites also have a strong relationship between pore type and throat size, though their maximum throat radius is 7 microns and some pore types have mean throat sizes less than 1 micron. The Reinecke Field data, coupled with data from studies on sandstones, suggests that throat size in all sedimentary rocks can be expected to be non-randomly associated with pore type. The non-random pore/throat association means that the pore types defined by image analysis represent fundamental elements of the porous microstructure and that variability in a wide range of physical properties is tied to variation in pore type abundance.

Dolomitization of lower Permian platform facies, Wichita Formation, north platform, Midland basin, Texas

Three specific occurrences, or types, of dolostone are recognized in regionally widespread platform dolostones in the Wichita Formation (Permian, Lower Leonardian) in the northern Midland basin of Texas: (1) non-porous dolostones composing supratidal-intertidal facies: rocks deposited and inherently overprinted by peritidal diagenetic features in this environment, (2) porous dolostones composing subtidal-intertidal facies: rocks deposited originally in subtidal environments and subsequently exposed and overprinted diagenetically on intertidal flats; and (3) porous subtidal dolostones: rocks deposited originally in subtidal environments and which were never exposed syndepositionally to peritidal diagenetic overprinting. Fine crystalline (5–40 μm) dolomites in all three dolostone types have mean δ18O composition of 0.6‰ PDB, but are enriched in δ18O by as much as 3.3‰ relative to estimated lower Leonardian sea water. These δ18O-enriched, fine crystalline dolomites are preserved mainly in the supratidal-intertidal dolostones, whereas more coarsely crystalline (> 40 μm, mean =78 μm) dolomites occur in the subtidal and subtidal-intertidal dolostones. Coarsely crystalline dolomites have δ18O compositions that are slightly lighter (mean=−0.25‰) than the fine crystalline dolomites, but are still enriched by a mean of 1.6‰ relative to Leonardian sea water. All dolomites are near-stoichiometric, with87Sr/86Sr within the range of values of lower Permian sea water. Coarse crystalline dolomites are more depleted in Sr, Mn, and Fe than fine crystalline dolomites although, regardless of crystal size, all dolomites contain less than 125 ppm Sr and less than 100 ppm Mn.

The Effect of Paleogeography on Erosion of Pennsylvanian Lowstand Carbonates in the Northern Midland Basin, with Modern Analogies: a New View of an Old Trend

The Effect of Paleogeography on Erosion of Pennsylvanian Lowstand Carbonates in the Northern Midland Basin, with Modern Analogies: a New View of an Old Trend

Reservoir Development in Brahaney Northwest and Patricia Fields, Northern Midland Basin, Texas: ABSTRACT

Porous pay zones in the Silurian-Devonian section of the northern Midland basin, Texas, vary stratigraphically, as well as structurally, with their locations beneath the pre-Woodford unconformity. These variations are related to at least two major periods of widespread pre-Woodford tectonism and erosion. A major unconformable surface, present at the top of the Lower Silurian Fusselman formation, was later modified by tectonism and erosion immediately preceding deposition of the Woodford Shale. In places where the Fusselman subcrops beneath the Woodford, its capacity for reservoir development is dependent upon the severity of geologic events that affected the formation during the two major tectonic/erosional events. Where the Wristen and Thirtyone formations subcrop, their reservoir capacity depends upon the extent of structuring and subsequent erosion immediately prior to Woodford deposition. Two pre-Woodford oil fields in the northern Midland basin illustrate geologic complexity that bears on the successful application of subsurface mapping in defining potential pay zones. Brahaney Northwest field in Yoakum County is productive from fractured, coarse crystalline Silurian-Devonian dolomites on subtle, fault-bounded structures. These structures, defined seismically on the base of the Woodford, do not reveal the more complex structural and stratigraphic variations within the reservoir itself. Patricia field in Dawson County ismore » productive from Fusselman carbonates where upper Fusselman structural and topographic relief coincides with post-Woodford faulting and low-relief anticlinal closure as defined at the base of the Woodford.« less

New Exploration Targets in Northern Midland Basin: Depositional and Diagenetic History of West Smyer Field: ABSTRACT

West Smyer field, Hockley County, Texas, produces from the upper part of the Wichita Group (Wolfcampian) in the northern part of the Midland basin. The field produces from a resedimented dolomitized grainstone at the base of the slope separating the Northwestern shelf from the deeper parts of the Midland basin. Since its discovery in 1984, the field has produced over 248,000 bbl of oil from just two wells. Shelf facies such as reefs or oolite shoals have been the primary exploration targets in the northern Midland basin. Areas of basinal facies remain relatively unexplored, but resedimented grainstones along the base of the slope are proven reservoirs in West Smyer and Levelland Northeast fields and potential reservoirs elsewhere. Laminated lime mudstones representing normal basinal sedimentation and fossiliferous grainstones composed of shallow-water sediments carried into the basin by turbidity currents alternate in core from West Smyer field. Fossils in the grainstones underwent micritization, silicification, and glauconitization while still residing on the shelf and were then resedimented into deeper water. During burial, the grainstones were cemented by calcite and then partially dolomitized. Next, the remaining calcite was dissolved, creating intraparticle, interparticle, and moldic pores. These secondary pores were then partially occluded by dolomite,more » followed, in turn, by pyrite and anhydrite, and later filled by hydrocarbons.« less

Lithologic and Geologic Characteristics of Silurian-Devonian and Woodford Formations, Northern Midland Basin, Texas: ABSTRACT

Lithologic and Geologic Characteristics of Silurian-Devonian and Woodford Formations, Northern Midland Basin, Texas: ABSTRACT

Evolution of San Simon Channel, Gaines County, Texas, Northern Midland Basin: ABSTRACT

Evolution of San Simon Channel, Gaines County, Texas, Northern Midland Basin: ABSTRACT

Evolution of Permian Carbonate Shelf and Foreshelf Detrital Systems, Midland Basin, Texas: ABSTRACT

A major phase of shelf progradation and consequent filling of the Midland basin began in the Early Permian. Prior to this time, shelf carbonate systems were mostly ineffective in generating coarse detritus in quantities sufficient to infill adjoining basins. Beginning in the Early Permian (Wolfcampian), however, the character of shelf and basin deposition was abruptly modified, in part because of faunal changes - proliferation of rock-forming biotic communities and the consequent potential for rapid shelf-marginal oversteepening - and the effects of sea level fluctuations and periods of shale influx. Shelf systems in the northern Midland basin and Eastern shelf evolved from ramps in the lowermost Wolfcamp to steep rimmed platforms by the lower Leonard. Shelf progradation into the Midland basin was cyclic, with extensive carbonate shelves having developed during sea level highstands and massive shale wedges deposited during alternate lowstands. Coarse megabreccia with markedly little sand dominates in the lower to middle Wolfcamp systems, despite the occurrence of ramps in this section. Such an anomaly can be explained by invoking widespread shelf wastage caused by the inherent instability and failure of the shale slopes on which these ramps were deposited. In certain middle Wolfcamp zones, thin shelf-ramp sections may be more » recognized only because any thick shelf-marginal buildups that may have been present have been displaced into adjoining basinal tracts. The evolution to rimmed-platform shelves by the lower Leonard strata, foreshelf debris occurs mostly as complexes of megabreccia wedges and aprons, anastomosing megabreccia, and sand-channel and lobe deposits derived from adjoining rimmed-platforms. Major variations exist in the gross geometries of foreshelf units and component reservoirs even laterally within rocks of the same age. « less

Depositional and Diagenetic Aspects of Siliciclastic and Carbonate Reservoirs in Glorieta Formation (Permian), Northern Midland Basin, Texas: ABSTRACT

The Glorieta formation is oil productive in the northern Midland basin. Production through 1982 totaled over 25 million bbl of oil. Carbonate as well as siliciclastic facies are productive in different locations on the shelf. This production is largely diagenetically controlled, with secondary porosity enhancement prevalent in both clastic and carbonate reservoir types. The Glorieta formation is composed of cyclicly deposited siliciclastics, carbonate, and carbonate-evaporite units. Environments of deposition range from supratidal sabkha through shallow subtidal to open-marine conditions. The siliciclastics are eolian-derived sediments that prograded onto the shelf of the northern Midland basin. The overall coarsening-upward sequence, the gently seaward dip of the clastics, and the open-marine characteristic of adjacent carbonate sediments suggest a subaqueous deposition similar to that described by Shinn along the leeward, southeast coast of Qatar Peninsula in the Persian Gulf. Diagenetic features affecting porosity development in the siliciclastic intervals include etching of quartz grains and penecontemporaneous precipitation of pore-filling, poikilotopic anhydrite cement. Subsequent partial dissolution of anhydrite cements increased porosity in clastic reservoir facies. The carbonate units have undergone pervasive dolomitization of mud matrix, leaching of allochems, and extensive anhydrite void filling. Replacement of dolomicrite by anhydrite and later solutioning of replacement fabric anhydrite contributed to secondary porosity in carbonate reservoirs. A better understanding of these diagenetic relationships could aid in predicting porosity trends in these distinctly different reservoir types within the Glorieta formation. End_of_Article - Last_Page 248------------

Stratigraphy and Depositional Mosaics of Lower Clear Fork and Wichita Groups (Permian), Northern Midland Basin, Texas

The stratigraphy, depositional environments, and reservoir potential of the Wichita Group and overlying Lower Clear Fork (Permian) in the northern Midland basin are described on the basis of seismic interpretations, log correlations, and lithologic analyses. The Wichita in this area is divided into a lower member of slope to basinal limestones and shales, and an upper member of shelf dolomites, varicolored shales, and evaporites. Only a starved lower Wichita section is present in areas to the south. Fusulinid evidence and physical correlations suggest that the Wolfcampian-Leonardian boundary occurs within the Wichita and ascends stratigraphically toward the north. These data, in conjunction with the upward-shoaling aspect of the Wichita, establish a progradational relatio between shelf facies of the upper member and slope to basinal facies of the lower member. The Lower Clear Fork beneath the Tubb member records continued southward progradation of similar shelf facies. These lithologies are represented in the basin by limestones and shales beneath, and possibly including lowermost Dean sandstones. Depositional systems of the Wichita and pre-Tubb Clear Fork sections are carbonate-dominated, rimmed shelves adjoining deeper basins. Periods of rapid progradation and offlapping shelf-edge accretion were cyclic, being coincident with periods of low sea level. The Tubb section records a change to a mixed siliciclastic and carbonate, rimmed shelf system. Deposition of shelf Tubb and basinal Dean facies was related to a mosaic of cyclic, reciprocal siliciclastic-carbonate sedimentation. Rapid shelf outbuilding occurred at low sea-level stands during the siliciclastic phases of sedimentation. The formation of the shallow North platform was more a consequence of constructional-sedimentary processes during the late Wolfcampian and early Leonardian than of structural influences. Over much of the northern Midland basin study area, potential stratigraphic hydrocarbon reservoirs are in Wichita and Lower Clear Fork strata. Such reservoirs occur as separate offlapping shelf-marginal (dolomitized) oolite grainstone shoals rather than organic buildups as was described in earlier studies.

Facies Patterns and Depositional Models of Permian Sabkha Complex--Red Cave Formation, Texas Panhandle: ABSTRACT

The Red Cave Formation (Permian, Leonard Series) in the Texas Panhandle consists of cyclic, red-bed clastic and carbonate-evaporite members that were deposited in an extensive coastal sabkha, desert wadi plain, and a carbonate inner shelf which bordered the northern Midland basin. Evaporite members were deposited in carbonate-evaporite crustal sabkhas and clastic members were deposited in mud-rich coastal to continental sabkhas. North to south, red-bed wadi-plain facies pass into coastal sabkha facies and inner-shelf dolomite facies. In a Randall County core, vertical sequences commonly include slightly fossiliferous, faintly laminated to burrowed dolomitic mudstone and pellet wackestone overlain by cross-laminated oolitic or pellet packstone to grainstone, followed by algal-laminated dolomitic mudstone and nodular anhydrite in dolomite matrix. A progradational carbonate shoreline is inferred, with supratidal or sabkha evaporite to intertidal algal-mat and sand-flat environments passing seaward into a shallow, muddy subtidal inner shelf. Mud-rich sabkha sequences culminate with red to green mudstone and anhydrite above shoreline carbonates. Carbonate and evaporite facies pinch out generally toward the northwe t and northeast into wadi-plain red beds. These facies include ripple-drift cross-laminated siltstone and sandstone deposited in braided fluvial channels, adhesion-rippled siltstone, and red to green mudstone deposited in mud-flat and interchannel environments. Desiccation features, intraclasts, root zones, and paleosol horizons attest to subaerial exposure and probable nonmarine conditions. Large-scale cyclicity of red-bed clastic and carbonate-evaporite members probably was controlled by the relative supply or fluctuating input of clastics to sabkhas by way of fluvial systems rather than by absolute sea-level changes. Partial modern analogs to Red Cave sabkha depositional models are the coastal mud flats and alluvial fans in the northwestern Gulf of California, tidal flats and an ephemeral stream delta (Wooramel delta) in Gladstone Embayment, Shark Bay, Australia, and the Trucial Coast sabkhas in the Persian Gulf. Each setting has certain facets that are remarkably similar to intepreted paleoenvironments and lithofacies of the Red Cave Formation. End_of_Article - Last_Page 761------------

Leonardian Strata in Northern Midland Basin of West Texas: ABSTRACT

Leonardian Strata in Northern Midland Basin of West Texas: ABSTRACT